Friday, September 8, 2017

Using your WLPC Odroid for APoS and wall attenuation measurements

If you are a WLAN professional, you have probably heard about other Wi-Fi Engineers using wall attenuation values when modeling the WLAN during your Ekahau ESS software to design the project. Short story, instead of using the default values in the software or doing a full AP-on-a-stick survey, the engineer takes a signal source and meter on-site and “measures” the wall attenuation to properly model and design the WLAN.

I was recently on-site during construction of an extremely large, brand new hospital – with the intention of measuring the wall attenuation values since construction was at the point where we could do so. In the past, I used a Buffalo access point that was powered by a cell phone charger – however this time I had an Odroid that I borrowed from a friend that attended the WLAN Professionals conference earlier this year. At the conference, they built and configured an Odroid single board computer that did all kinds of nifty things that a WLAN Engineer might want.

Now back to measuring wall attenuation! In the past, I used a Buffalo access point and my Netscout Aircheck G2 to get the job done. If you own Ekahau ESS and are not sure how to measure wall attenuation, the process of measuring walls is taught in the Ekahau ECSE class.

This time, I had the Odroid on a battery, along with @WiFi_Princesa at the helm of the G2 and my Android with Wi-Fi Analyzer on my clipboard. During the wall measuring process, I discovered that I was getting the same decibel values that I would expect if I was doing an AP-on-a-stick survey. I did not expect the same results, since I assumed the Odroid would have a much smaller footprint than an actual enterprise access point’s coverage area.

That got me thinking. I wanted to know the actual coverage area of the Odroid so I could compare it to an enterprise access point, such as a Cisco 3602i series. When I do an AP-on-a-stick survey, I normally set my AP to channel 36, with a power level of 3. I equate the power level of 3 to approximately 11 dBm.

I took the Odroid to a validation survey the following day, and set the AP on the ceiling to a 20 MHz channel width with a power level of 3. I set the Odriod directly beneath the AP, and proceeded to do my validation survey. After playing with the output power of the Cisco AP on the ceiling, I determined that the Odriod has the same coverage pattern as a Cisco AP on UNII-1 with power level of 3.

Here are the heat maps of the Cisco 3602i and the Odroid. Conclusion – I think I can use an Odroid to simulate a Cisco 3602i’s coverage pattern when doing both APoS and wall attenuation measuring missions.

Here is the Cisco 3602i at -65 dBm

Here is the Odroid at -65 dBm

What do you think? Will you use an Odoid to simulate an enterprise AP?